Heated controlled deflection roll

ABSTRACT

A heated controlled deflection roll including a center support and a rotatable roll shell surrounding the center support. A shoe assembly connects the center support and the inside surface of the rotatable roll shell. The shoe assembly includes a shoe in contact with the inside surface of the rotatable roll shell and a bladder positioned between the shoe and the center support. The shoe assembly has a length substantially equal to a length of the inside surface of the rotatable roll shell. Free space within a chamber within the rotatable roll shell is filled with a heat transfer fluid and heater elements. The heater elements have angled fins for directing the flow of the heat transfer fluid in a helical pattern towards one end of the rotatable roll shell. The heat transfer fluid returns to the opposite end of the chamber through a passage through the center support.

FIELD OF INVENTION

[0001] The present invention relates to a heated controlled deflectionroll useful in pairs or in combination with other types of rolls for niprolling fibrous materials such as nonwoven webs.

BACKGROUND OF THE INVENTION

[0002] Pairs of mated rolls forming a nip through which a traveling webpasses are well known in the field of paper making, and more recently,in the textile and nonwovens industries to remove water from the web,calender, bind, or emboss the fibrous web. In such cases the nippressures cause the rolls to deflect to an extent that some form ofcompensation for the roll deflection must be provided. Withoutcompensation the resulting nip pressure will be extremely non-uniformacross the width of the rolls.

[0003] One common way of compensating for roll deflection is to grind a“crown” on one of the mated rolls. Crowning is a common method ofdeflection compensation due to its relatively lower cost. A “crown” isdefined as a slight and gradual increase in the diameter of the rollshell near the center of the roller as compared to either end. However,the shape of the roll crown is difficult to identify because the crownmust precisely match the shape of the deflection curve if a uniform nipis to result. Even when the shape is identified by several iterations ofgrinding and observing the resulting nip pressure profile, the precisionrequired in the grinding process is also difficult to consistentlyattain.

[0004] Another disadvantage of roll deflection compensation by crowningis that, once crowned, the roll is capable of providing a uniform nippressure only at the particular value of nip pressure for which it wasplanned and calculated. A lower nip pressure will result in too muchpressure at the center, and a higher nip pressure will result in a muchhigher pressure at the roll ends. Being limited to one pressure aftergrinding a roll to a particular amount of crown is a disadvantage formost of the processes using nip rolls.

[0005] Another method of compensating for roll deflection is rollbending. Roll bending is commonly used in the textile and plasticsindustries where highly uniform nip pressures are not required. Abending moment is placed on the roll ends by two sets of bearings andextended roll journals. However, the resulting shape of the rollstypically does not fit the deflection curves exactly.

[0006] Still another method used in the textile industry is to use rollsof sufficiently large diameter and then cover one or both rolls with anelastomeric material. The large roll diameters and flexible coversmitigate the inherent non-uniformity of the nip pressure. This method isgenerally limited to processes that allow the use of a flexible cover,where exact pressure uniformity is not required, and when a heated nipis not required.

[0007] Self-loading controlled deflection rolls use internal pistons or“shoes” to move the roll shell into the mated roll. The stationarypistons or shoes at the nip centerline press on the rotating roll shelland counterbalance the nip pressure, thereby forcing the controldeflection roll shell into the mated roll shell as needed to compensatefor deflection of the mated rolls. Controlled deflection rolls aregenerally more complex than previously discussed rolls and thus have ahigher cost. A commonly used controlled deflection roll is commonlyreferred to as a “swim roll.” This type of roll uses a pressure of abouttwo or three bars in the upper half of an annulus formed by the rotatingshell and the non-rotating center support. Axial seals at the 3:00 and9:00 o'clock positions run the length of the roll shell/center support.Circumferential seals on each end are also employed. This design isgenerally commercially limited to a 505 millimeter (19.9 inch) maximumdiameter, which limits its use for high speed bonding of melt spunfibers which typically require larger roll diameters to increase thebonding time within the nip. Another disadvantage of this design whenused as a heated roll is the maintenance, safety, and housekeepingconcerns associated with pumping hot oil at high pressures.

[0008] The pistons used in current controlled deflection rolls aretypically loaded with hydraulic pressure supplied by pumps external tothe roll. The oil is brought to cavities at the top of the pistons. Thecavities are formed on one side by the rotating shell. The cavities aredesigned to balance the piston force, such that the pistons float on ahydrostatic cushion of oil. Some oil also flows out of the cavitylubricating the piston surface in contact with the rotating shell.Stationary crescent shaped “shoes” generally use internally generatedhydrodynamic oil pressure to lubricate the shoe/shell interface andprevent metal to metal contact. Hydrodynamic oil pressure is createdwhen one moving plate (the roll shell) and one stationary plate (theshoe) are at a slight angel to each other, creating a wedge as the oilis drawn into the diminishing clearance between the two plates by themoving plate. Pressures in excess of 1000 pounds per square inch can begenerated by this method.

[0009] Current controlled deflection rolls are typically limited tosmaller diameters as well as low operating temperatures. Additionally,controlled deflection rolls are typically expensive due to thecomplexity of the loading mechanisms. The cost of typical currentcontrolled deflection rolls prohibits the use of the rolls in pairs,which is generally most desirable. Using controlled deflection rolls inpairs is ideal for nip uniformity since both roll shells can remainstraight, with zero bending stress (and strain), and zero shear stress(and strain) and therefore neither roll has to conform to the other.

[0010] Current commercial heated controlled deflection rolls includeexternal oil heaters and pumps, as well as the piping that is used toconnect these external parts. The high pressure, high temperature pumpsand filters are difficult to maintain and typically have some oilleakage. Roll changes are difficult because disconnecting the roll fromthe external piping causes some loss of oil. The loss of oil from pumpseals, roll changes, and other maintenance operations are a housekeepingand safety concern.

[0011] There is a need for a less complex, less expensive, largediameter, heated, controlled deflection roll. There is particularly aneed for low cost controlled deflection rolls that allow for costefficient use in pairs. There is a need for a self-contained controlleddeflection roll that does not require many or any external pumps orheaters, and therefore can more easily be added or removed from amachine frame.

SUMMARY OF THE INVENTION

[0012] A general object of the invention is to provide improved heatedcontrolled deflection rolls. A more specific objective of the inventionis to overcome one or more of the problems described above.

[0013] A general object of the invention can be attained, at least inpart, through a fluid-filled controlled deflection roll includinginternal heating elements. The heated controlled deflection rolls ofthis invention utilize a hydrodynamic shoe assembly that extendssubstantially the full length of an inside surface of the roll shell.

[0014] In one embodiment of this invention, a controlled deflection rollincludes a center support and a rotatable roll shell including an insidesurface surrounding the center support. A shoe assembly is between thecenter support and the inside surface of the rotatable roll shell. Theshoe assembly includes a shoe in contact with the inside surface of therotatable roll shell and a bladder positioned between the shoe and thecenter support. The shoe assembly has a length substantially equal to alength of the inside surface of the rotatable roll shell, and includes asingle shoe and a single bladder that both extend a length substantiallyequal to a length of the inside surface of the rotatable roll shell.

[0015] In another embodiment of this invention, the controlleddeflection roll includes a center support, a shoe assembly incombination with the center support, and a rotatable roll shell,surrounding the center support and having an inside surface contactingthe shoe assembly. An end element surrounds the center support on eachend of the rotatable roll shell, and the rotatable roll shell and theend elements enclose a chamber. A heat transfer fluid is containedwithin the chamber. The heat transfer fluid is driven by the insidesurface of the rotatable roll shell and flows within the chamber aroundthe center support in a direction of rotation of the rotatable shell.

[0016] In yet another embodiment of this invention, a controlleddeflection roll includes a center support, a rotatable roll shellincluding an inside surface surrounding the center support, and an endelement surrounding the center support on each end of the roll shell.The rotatable roll shell and the end elements enclose a chamber. Thecenter support extends through the chamber and out past each of the endelements. The chamber encloses at least one heater element and a heattransfer fluid. At least one of the center support and the at least oneheater element includes at least one angled fin thereon for mixing anddirecting the flow of the heat transfer fluid within the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] These and other objects and features of this invention will bebetter understood from the following detailed description taken inconjunction with the drawings, wherein:

[0018]FIG. 1 shows a cross section view of a controlled deflection rollaccording to an embodiment of this invention.

[0019]FIG. 2 shows a partial sectional view of a controlled deflectionroll according to an embodiment of this invention.

[0020]FIG. 3 shows a partial sectional view of a controlled deflectionroll and frame according to an embodiment of this invention.

[0021]FIG. 4 shows a partial sectional view of a shoe and a rotatableroll shell of a controlled deflection roll according to an embodiment ofthis invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0022]FIG. 1 shows a cross-sectional view of a controlled deflectionroll 10 of one embodiment of this invention. The controlled deflectionroll 10 of this invention can be used in combination with a second rollto create a nip between the pair of rolls through which a fibrous webmaterial, such as a nonwoven fabric, is run. The controlled deflectionrolls of this invention can be used in combination with various types ofrolls known in the art, such as plain cylindrical heated rolls or othertypes of controlled deflection rolls, and is desirably used incombination with a second, similar controlled deflection roll of thisinvention.

[0023] The controlled deflection roll 10 includes a center support 12extending through the controlled deflection roll 10. A rotatable rollshell 14 is positioned around the center support 12, such that an insidesurface 16 of the rotatable roll shell 14 surrounds the center support12. The inside surface 16 extends between two end elements 15, one oneach side of rotatable roll shell 14. The center support 12 desirablyextends beyond the opposite end elements 15 of the rotatable roll shell14 for connecting the controlled deflection roll 10 to a machine frame,such as supports 50 as shown in FIG. 3. The center support 12 isstationary and fixed to the machine frame, and will support thecontrolled deflection roll 10 within the desired ranges of deflection.The center support 12 is desirably made of materials such as steel orcast iron.

[0024] The rotatable roll shell 14 can vary in diameter, and is suitablyabout 400 to 2000 millimeters, and desirably about 600 to 1000millimeters. The rotatable roll shell 14 can be made of materials suchas alloy steel or cast iron. The nip created by the rotatable roll shelland a second roll shell can be used for calendering, bonding, orembossing a fibrous material traveling through the nip. An externalsurface 17 of the rotatable roll shell 14 can be smooth, rough, orinclude a pattern for embossing fibrous webs.

[0025]FIG. 1 shows a shoe assembly 20 including a shoe 22 in contactwith the inside surface 16 of the rotatable roll shell 14 and a bladder24 positioned between the shoe 22 and the center support 12. The shoeassembly 20, including both the shoe and the bladder, has a lengthsubstantially equal to a length of the nip load, which desirably runsabout 8 to 20 inches less than the length of the inside surface 16 ofthe rotatable roll shell 14. In one embodiment of this invention, theshoe assembly 20 has a length substantially equal to a length of theinside surface 16 of the rotatable roll shell 14, and includes a singleshoe 22 and a single bladder 24 that both extend a length substantiallyequal to a length of the inside surface 16 of the rotatable roll shell14. The shoe can be made from materials such as brass, bronze, castiron, or steel, and is desirably made from brass or bronze in order toprovide a wearing surface against the rotatable shell. As shown in FIGS.2 and 3, the rotatable roll shell 14 of this invention has an endelement 15 on each of opposite ends of the rotatable roll shell 14enclosing a chamber 26 around a length of the center support 12. Thelength of the shoe assembly 20 desirably runs approximately the lengthof the nip load between the two end elements 15. The end elements 15 caninclude various designs and parts; however each of the end elements 15typically includes at least one movable part, such as a roller bearing,that allows the rotatable roll shell 14 to rotate around the centersupport 12, and seals which seal the enclosed chamber 26 for containinga heat transfer fluid. As the end elements 15 include moving partsallowing the rotatable roll shell 14 to rotate, it is desirable that theends of the non-rotating shoe assembly 20 do not contact the endelements 15. Therefore, the shoe assembly 20 and the end elements 15 aredesirably separated by a minimal space.

[0026] The shoe assembly 20 is connected to the center support 12 viathe bladder 24 and is guided and restrained by roller elements 11 oneither side of the shoe 22 and fastened to the center support 12. Theshoe 22 contacts the inner surface of the rotatable roll shell 14 and isground to a diameter slightly less than that of the inside surface 16.The shoe assembly 20 exerts a load on the rotatable roll shell 14 in adirection towards a nip between the controlled deflection roll 10 and amated second roll. The bladder 24 is made of an expandable elastomericmaterial such as VITON®, a fluroelastomer available from DuPont DowElastomers, LLC, or silicone, which allows the bladder 24 to expand whena pressure within the bladder is increased, and which allows the bladder24, and therefore controlled deflection roll 10, to be used in hightemperature applications. The bladder 24 exerts an increased load on theshoe 22 when the pressure within the bladder is increased. Oppositely,the load on the shoe 22 can be decreased by decreasing the pressurewithin the bladder 24. The controlled deflection roll 10 of thisinvention can be used to provide nip loading up to about 3500 pounds perlinear inch and desirably between about 200 to 1500 pounds per linearinch. The bladder 24 contains one of a gas or fluid such as oil.Desirably the bladder is pressurized with the same heat transfer fluidused to fill the chamber 26 between the rotatable shell 14 and thecenter support 12. The pressure within the bladder 24 is controlled by acompressed air regulator 27 which feeds air directly to the bladder, ordesirably, as shown in FIG. 3, to an “air over oil” device 25, such asknown in the art, external to the roll which contains the same heattransfer fluid used inside the chamber 26, such that the air pressureabove the heat transfer fluid maintains its pressure and allows thefluid to flow in or out of the bladder 24 as needed to maintain thedesired pressure.

[0027] The bladder 24 exerts a load on shoe 22 which in turn exerts aload on the rotatable roll shell 14. As shown in FIG. 4, the shoe 22desirably includes a circular portion oriented towards the insidesurface 16 of the rotatable roll shell 14. The radius of a curvature ofthe shoe 22 must be manufactured to a radius slightly less than thediameter of the inside surface 16 of the rotatable roll shell 14. Inorder to create a desired high hydrodynamic oil pressure, and thus asafe operating condition for the lubrication of the shoe, the differencein radii will result in a desirable average gap at the sides 38 of theshoe 22 which is 2.2 times the gap at the center 40 of the shoe 22.However, the gap at the center 40 of the shoe 22 is a function of: 1)the load of the shoe; 2) the viscosity of the heat transfer fluid; and3) the surface speed of the inside surface 16 of the rotatable rollshell 14. Therefore, obtaining the desired gap ratio of 2.2 can bemaintained only for one set of conditions.

[0028] As discussed above, the controlled deflection roll 10 includes anend element 15 at each end of the rotatable roll shell 14. As shown inFIGS. 2 and 3, the end elements 15 surround the center support at eachend of the rotatable roll shell 14 and include movable parts, such asroller bearings 48. The roller bearings 48 allow the rotatable rollshell 14 to rotate around the center support 12. The rotatable rollshell 14 and the end elements 15 enclose a chamber 26 surrounding aportion of the center support 12 between the end elements 15. Thechamber 26 includes an annulus that contains, and is desirably filledwith, a heat transfer fluid 28. “Annulus” refers to an interstitial freespace within the chamber 26 around the components of the controlleddeflection roll 10 within the chamber 26. The size and dimensions of theannulus depends on the size and shape of the components of thecontrolled deflection roll 10 within the chamber 26, such as the shoeassembly 20 and the center support 12. The heat transfer fluid 28 freelyflows within the annulus of the chamber 26. Upon rotation of therotatable roll shell 14, the heat transfer fluid 28 will flow around thecenter support 12, as well as around the other components in the chamber26, in a direction of rotation of the rotatable roll shell 14. The heattransfer fluid 28 provides lubrication between the shoe 22 and theinside surface 16 and can be used to transfer heat to the rotatable rollshell 14 from one or more heater elements 30 within the chamber 26. Theheat transfer fluid 28 of this invention includes, without limitation,oils, synthetic oils or heat transfer fluids. Desirably, the bladder 24contains the same material as the heat transfer fluid 28 so that if asmall leak occurs in the bladder 24, the leak will not displace the heattransfer fluid 28 with a different material such as air.

[0029] In one embodiment of this invention, the controlled deflectionroll 10 includes a shoe assembly bypass 32 in combination with the shoeassembly 20. The heat transfer fluid 28 flows in a direction of rotationof the rotatable roll shell 14 and lubricates the surface of shoe 22exerting force on the inside surface 16 of the rotatable roll shell 14.The amount of heat transfer fluid 28 that passes between the shoe 22 andthe inside surface 16 is minimal compared to the total amount of heattransfer fluid 28 which is desirably flowing circumferentially, and thusthe shoe assembly bypass 32 allows the flow of heat transfer fluid 28 tocontinue through the chamber 26 and around the center support 12. Thusthe shoe assembly bypass 32 prevents an obstruction of the flow of theheat transfer fluid 28 caused by the shoe 22 and the shoe assembly 20.The shoe assembly bypass 32 is shown in FIGS. 1 and 3 between thebladder 24 and the center support 12. The shoe assembly bypass 32 allowsthe heat transfer fluid 28 to flow between the bladder 24 and the centersupport 12. The shoe assembly bypass 32 can include channels between theconnections connecting the bladder 24 and the center support 12 or bechannels formed in the center support 12. One skilled in the art willappreciate the various configurations possible for the shoe assemblybypass 32, such as channels between the bladder 24 and the shoe 22,preformed passageways through the bladder itself, and combinations ofthese embodiments.

[0030] The controlled deflection roll 10 includes at least one heaterelement 30 within the chamber and in contact with the heat transferfluid 28. FIG. 1 shows two heater elements 30 located between the centersupport 12 and the rotatable roll shell 14. As will be appreciated byone skilled in the art, the heater elements 30 can include variousconfigurations. In one embodiment of this invention, the heater elements30 desirably run the length of the center support 12 within chamber 26.The heater elements 30 are suitably electric heater elements and madefrom a conductive material such as aluminum. The heater elements 30 areshown in FIG. 1 as crescent shaped to fit between the center support 12and rotatable roll shell 14. The size and shape of the heater elementscan vary depending on the size and shape of the center support 12 and/orthe rotatable roll shell 14.

[0031] The heat transfer fluid 28 passes over the heater elements 30 asit circumferentially flows through the chamber 26 around the centersupport 12. The heat produced by the heater elements 30 heats the heattransfer fluid 28 and the heat transfer fluid 28 in turn heats therotatable roll shell 14. Suitably the heater elements 30 and the heattransfer fluid 28 heat an outer surface of the rotatable roll shell 14to obtain a temperature of at least about 100° C., more desirably about100° C. to 260° C. The controlled deflection roll 10 of this inventioncan include an external heat transfer fluid expansion tank 38 connectedto the chamber 26 by a heat transfer fluid expansion line 39. Theexpansion tank holds additional heat transfer fluid 28. If the heattransfer fluid 28 expands upon heating, an amount of the heat transferfluid 28 enters the expansion tank 38 through the expansion line 39thereby maintaining a desired low pressure of the heat transfer fluid 28within the chamber 26. The expansion tank can be located above thecontrolled deflection roll or include an air cushion (not shown) tobalance the pressure of the heat transfer fluid 28 in the expansion tankwith the pressure in the chamber 26. As shown in FIG. 3, the expansionline 39 can enter the center support 12 at one end and connect tochamber 26. In one embodiment the heat expansion tank 38 is locatedwithin chamber 26. In one embodiment of this invention,, the heatexpansion tank 38 and the pump 25 for the bladder 24 are both within thechamber 26, providing a self-contained controlled deflection roll 10.The self-contained controlled deflection roll 10 allows for easy removaland roll changes.

[0032] As shown in FIG. 3, the rotatable roll shell 14 rotates aroundthe center support 12 via a motor 40 and gears 42 and 44. The motor 40turns a shaft 46 including a first gear 42 that corresponds to a secondgear 44 connected to one end element 15 of the controlled deflectionroll 10. FIG. 3 shows the gears 42 and 44 as spur gears however othergear configurations can be used, such as two helical gears. The motor 40rotates the rotatable roll shell 14 around roller bearings 48 thatextend around the center support 12 at both end elements 15 of therotatable roll shell 14. The center support 12 does not rotate and isfixed to a support 50 at each end of center support 12. The end elements15 are desirably sealed to avoid leaking the heat transfer fluid 28.

[0033] As the rotatable roll shell 14 rotates around the center support12, the rotatable roll shell 14 produces drag forces that cause the heattransfer fluid 28 to flow in the same circumferential direction. Theresulting flow of the heat transfer fluid 28 has characteristicsdescribed by Couette flow dynamics. “Couette flow” refers to themovement of a fluid between two surfaces, wherein at least one surfaceis moving. The heat transfer fluid 28 in contact with the rotatable rollshell 14 moves in a direction of rotation of the rotatable roll shell14. The heat transfer fluid 28 in contact with the center support 12, orother stationary surfaces within the chamber 26, does not move with thesame velocity, if at all, as the heat transfer fluid 28 toward therotatable roll shell 14 due to the viscosity of the heat transfer fluid28. The result is a gradient of circumferential flow velocity of theheat transfer fluid 28 between the rotatable roll shell 14 and thecenter support 12.

[0034] The dimensions of the annulus of chamber 26, as well as thegeometry of any mixing fins, can affect the amount of turbulence in theflow of the heat transfer fluid 28. In addition, the dimensions of theannulus of chamber 26 can affect the motor power required to rotate therotatable roll shell 14, as the degree of turbulence of the heattransfer fluid will affect the required motor power. A smallerdimensioned annulus can cause a laminar flow of the heat transfer fluid28. Oppositely, a larger dimensioned annulus allows for a more turbulentflow. Laminar flow of the heat transfer fluid reduces the powernecessary to rotate the rotatable roll shell 14 as compared to turbulentflow. Turbulent flow, however, has the advantage of more efficient heattransfer from the heating elements 30 to the heat transfer fluid 28, aswell as from the heat transfer fluid 28 to the rotatable roll shell 14.Also, the motor power needed to shear the heat transfer fluid 28typically results in an amount of heat energy in the heat transfer fluid28. Thus, the controlled deflection roll 10 can include various annulusconfigurations including smaller annulus dimension in areas of chamber26 for reducing the required motor power and larger annulus dimensionsin other areas of chamber 26 to promote efficient heat transfer. In oneembodiment of this invention, a larger dimensioned annulus of chamber 26is used in combination with a heater element 30 to promote efficientheat transfer through turbulent flow of the heat transfer fluid 28. Thedimensions of the annulus of chamber 26 can be controlled by varying thesize of the components of the controlled deflection roll 10 withinchamber 26, such as the size and shape of the center support 12 andheater elements 30.

[0035] Discontinuous surfaces, such as fins extending from a surfacewithin the chamber 26 can also be used to create or enhance flowturbulence in the annulus. In one embodiment of this invention, thecontrolled deflection roll 10 includes at least one heater element 30having fins which increase turbulent flow over the at least one heaterelement 30. The fins of one embodiment of this invention have a heightof about 0.63 centimeters, and are suitably about 0.3 to 1.5centimeters.

[0036]FIG. 2 shows the heater elements 30 including a plurality ofangled fins 34. The controlled deflection roll 10 in FIG. 2 rotates in adirection shown by the arrows A. The rotation of the rotatable rollshell 14 causes the heat transfer fluid to flow in a similar rotationaldirection shown by arrows B. The angled fins 34 change in the directionof the flow as shown by the arrows C. The angled fins 34 causeturbulence in the flow of the heat transfer fluid 28 and direct the flowin a helical pattern in a direction towards one end of the chamber 26.The helical flow resulting from angled fins 34 provides efficientheating over a length of the rotatable roll shell 14. In on embodimentof this invention the angle of the angled fins 34 are about 0 to 80degrees from a line parallel to the center support 12, more suitablyabout 30 to 70 degrees, and desirably about 40 to 60 degrees. The centersupport 12 can also include fins for promoting turbulent flow. As shownin FIG. 1, the fins on the center support 12 are angled fins 34 having asame or different angle than the angled fins 34 on the heater elements30. The fins on the center support 12 can also be straight fins parallelor perpendicular to the rotational direction of the rotatable roll shell14.

[0037] The angled fins 34 direct the flow of the heat transfer fluid 28in a helical pattern around the center support 12 from one end of thechamber 26 to an opposite end of the chamber 26. The controlleddeflection roll 10 shown in FIG. 1 includes a heat transfer fluidpassage 36. As shown in FIG. 3, the heat transfer fluid passage 36extends through a length of the center support 12 from at least onefirst opening 35 between the center support 12 and the end element 15proximate to one end of the chamber 26 to at least one similar secondopening 37 at the opposite end of the chamber 26. The heat transferfluid 28 can be directed axially to one end of the chamber 26 by theangled fins 34. Reaching the end of the chamber 26 the heat transferfluid enters the first opening 35 of the heat transfer fluid passage 36and flows through the passage 36 towards the opposite end of the chamber26 and reenters the chamber 26 at the second opening 37 of the heattransfer fluid passage 36. The heat transfer fluid passage 36 allows fora continuous helical flow of heat transfer fluid 28 through chamber 26.

[0038] While in the foregoing specification this invention has beendescribed in relation to certain preferred embodiments thereof, and manydetails have been set forth for purpose of illustration, it will beapparent to those skilled in the art that the invention is susceptibleto additional embodiments and that certain of the details describedherein can be varied considerably without departing from the basicprinciples of the invention.

What is claimed is:
 1. A controlled deflection roll, comprising: acenter support; a rotatable roll shell including an inside surfacesurrounding the center support; and a shoe assembly including a shoe incontact with the inside surface of the rotatable roll shell and abladder positioned between the shoe and the center support, the shoeassembly having a length substantially equal to a length of the insidesurface of the rotatable roll shell.
 2. The controlled deflection rollof claim 1, wherein the bladder contains one of a gas and a fluid. 3.The controlled deflection roll of claim 2, wherein the bladder exerts aload on the shoe when a pressure within the bladder is increased.
 4. Thecontrolled deflection roll of claim 1, further comprising an end elementsurrounding the center support on each end of the roll shell, therotatable roll shell and the end elements enclosing a chamber containinga heat transfer fluid.
 5. The controlled deflection roll of claim 4,wherein the heat transfer fluid flows within the chamber around thecenter support in a direction of rotation of the rotatable shell.
 6. Thecontrolled deflection roll of claim 5, further comprising a shoeassembly bypass in combination with the shoe assembly.
 7. The controlleddeflection roll of claim 6, wherein the shoe assembly bypass allows theheat transfer fluid to flow between the bladder and the center support.8. The controlled deflection roll of claim 4, further comprising atleast one heater element within the chamber and in contact with the heattransfer fluid.
 9. A controlled deflection roll, comprising: a centersupport; a shoe assembly in combination with the center support; arotatable roll shell including an inside surface contacting the shoeassembly, the rotatable roll shell surrounding the center support; anend element surrounding the center support on each end of the rollshell, the rotatable roll shell and the end elements enclosing achamber; and a heat transfer fluid within the chamber, wherein the heattransfer fluid flows within the chamber around the center support in adirection of rotation of the rotatable shell.
 10. The controlleddeflection roll of claim 9, further comprising a heat transfer fluidexpansion line connecting the chamber to a heat transfer fluid expansiontank external of the chamber.
 11. The controlled deflection roll ofclaim 9, further comprising at least one heater element within thechamber and in contact with the heat transfer fluid.
 12. The controlleddeflection roll of claim 11, further comprising fins on at least one ofthe heater element and the center support.
 13. The controlled deflectionroll of claim 12, wherein the fins are configured to direct the flow ofthe heat transfer fluid in a helical pattern around the center supportfrom one end of the chamber to an opposite end of the chamber.
 14. Thecontrolled deflection roll of claim 13, further comprising a heattransfer fluid passage extending through a length of the center support.15. The controlled deflection roll of claim 9, wherein the shoe assemblyhas a length substantially equal to a length of the rotatable rollshell.
 16. The controlled deflection roll of claim 15, furthercomprising a shoe assembly bypass in combination with the shoe assembly.17. A controlled deflection roll, comprising: a center support; arotatable roll shell including an inside surface surrounding the centersupport; an end element surrounding the center support on each end ofthe roll shell, the rotatable roll shell and the end elements enclosinga chamber; at least one heater element within the chamber; a heattransfer fluid within the chamber; and at least one angled fin on atleast one of the center support and the at least one heater element fordirecting a flow of the heat transfer fluid within the chamber.
 18. Thecontrolled deflection roll of claim 17, further comprising a heattransfer fluid passage extending through a length of the center support.19. The controlled deflection roll of claim 17, further comprising ashoe assembly between the center support and the roll shell.
 20. Thecontrolled deflection roll of claim 19, further comprising a shoeassembly bypass in combination with the shoe assembly.
 21. Thecontrolled deflection roll of claim 17, wherein the at least on anglefin is configured to cause turbulence in the heat transfer fluid flow asthe heat transfer fluid flows over the surface of the heater element.22. The controlled deflection roll of claim 17, wherein the heattransfer fluid fills an annulus of the chamber.
 23. The controlleddeflection roll of claim 17, wherein the heat transfer fluid is an oil.